MEXICO CITY — A contingent of elderly Mexico City residents will wear smog-detecting vests to study the effects of the sprawling capital’s polluted air on people over 65, the nation's Health Department has announced.

Thirty-two volunteers from two neighborhoods will strap on blue jackets weighing about 5 pounds and fitted with filters measuring six kinds of air pollution, said Miguel Lombera, coordinator of department’s risk and research division.

The $827,000 joint federal and city study will begin in August and produce findings by the end of the year, Lombera told reporters Tuesday.

“We want to monitor an individual’s personal reaction to the pollution,” Lombera said. “What effect does the air have on one individual versus another.”

Journals will be keptThe volunteers, all of whom have been certified as nonsmokers in good health, will keep a journal of their daily activities while wearing the vests, letting authorities know if they rode city buses — many of which use rooftop exhaust systems that belch black soot — or walked along busy avenues choked with car exhaust.

“A daily routine also helps us monitor the effects of, say, tobacco smoke in a small restaurant,” Lombera said.

All volunteers will wear their vests for 24 hours straight, then take a break while authorities spend a day analyzing the previous period’s findings.

They all must live close to the city’s main air-monitoring stations to allow officials to compare the levels of smog detected by their vests with the pollution contained in the air.

Plan to test children laterIn 2005, officials hope to expand the program to children ages 12 and 13 living in other parts of the city.

Health Department officials said the study’s timing does not mean air pollution is getting worse in Mexico City. In fact, things have been improving steadily since local officials first began introducing programs to control smog in the 1980s.

At least 61 days met “satisfactory” standards for ozone levels in the metropolitan area in the first five months of this year, which included much of the annual March-July smoggy season. There were only 80 such days all of last year.

Dust particles forced a smog alert just before Christmas last year, but constant warnings about dangerous levels of smog are no longer monthly occurrences, as they were 10 years ago, Lombera said.

In the future, officials hope to conduct similar human smog-detector studies cities like Tijuana and Ciudad Juarez, on the U.S. border, as well as other large, metropolitan areas like Guadalajara and Monterrey.